Fluorinated olefins, in particular tetrafluoroethylene (TFE), are important raw materials for the preparation of fluoropolymers. TFE is commonly prepared from fluorine and chlorine containing starting materials (e.g. R22=CHClF2), which are of environmental concern, for example for their potential effect on ozone depletion in the atmosphere. Therefore, there exists a need for alternative ways of producing TFE.
TFE and other fluoroolefins are known to be derivable from thermal decomposition (pyrolysis) of fluoropolymers, such as polytetrafluoroethylene.
Fluoropolymers, i.e. polymers having a fluorinated backbone, have been used in a variety of applications because of several desirable properties such as heat resistance, weatherability, UV-stability and resistance to harsh chemical environments and have found widespread application as starting materials for household and chemical appliances, such as for example coatings for cookware, as raw material for making O-rings, hoses or sealings for example of fuel systems, or as textures in the building industries. Various fluoropolymers and their applications are, for example, described in “Modern Fluoropolymers”, edited by John Scheirs, Wiley Science 1997, “Fluoropolymer Applications in Chemical Processing Industries, edited by Sina Ebnesajjad and Pradip Khaladkar, William Andrew Inc, Norwich, N.J., USA, 2005.
Several technologies for pyrolysing fluoropolymers have been described, for example pyrolysis by steam (U.S. Pat. No. 3,832,411 to Arkles et al), by radio frequencies (U.S. Pat. No. 6,797,913 to van der Walt et al) or by electric arcs (international patent application WO 01/58840 to van der Walt et al). These technologies, however, may lead to low conversion and/or involve high energy consumption. Furthermore, repolymerization may take place within the described processes which may lead to clogging of the equipment and increased working-up procedures. Moreover, these technologies may require elaborate equipment and complex monitoring.
Surprisingly it was found, that at least of the above-mentioned drawbacks could be overcome by pyrolysis in the presence of microwave irradiation, in particular while contacting the fluorinated material to be pyrolysed in the presence of microwave-active particles.